An optical transceiver is a physical device that connects a host interface (i.e., host board) to a fiber optic network or other communication system. In the present invention, the transceivers are optoelectronic transceivers, which means that data is transmitted to and from the transceivers electrically at one end, and optically at the other end. In systems that use optoelectronic transceivers, it is often desirable to pack as many transceivers as possible on the edge (i.e., back face) of a host board to maximize the communication bandwidth of the systems. Very narrow transceivers that can be packed at a dense pitch are, therefore, desirable. As a result, host boards are often configured to accommodate a series of small form factor (i.e., narrow or single-width) transceivers.
Such host boards are only viable, however, if each transceiver connected thereto has a common form factor (i.e., similar width). But there exist a variety of transceiver designs to address different needs. For example, vertical-cavity surface emitting lasers (VCSELs) are often used for very short optical links (i.e., the distance light must travel from a light source to a receiver) of up 500 meters. Simple Fabry-Perot 1310 nm lasers are often used for optical link lengths of up to 20 km in systems designed for 1 Gigabit per second data rates or 2 km in systems designed for 10 Gigabit per second data rates. But for much longer optical links with lengths of up to 80 km at 1 Gb per second data rates and up to 10 to 40 km at 10 Gb per second data rates and where it is desired to combine signals of different wavelengths, transceivers integrating DFB lasers with temperature controllers and avalanche photo diodes (APDs) are often required.
The VCSEL and Fabry-Perot laser based transceivers can often be constructed in very narrow widths (i.e., small form factor designs or single-width transceivers), but more complex designs, such as transceivers integrating DFB lasers with temperature controllers and avalanche photo diodes, often require a greater widths (i.e., larger form factor designs) to accommodate the extra circuitry and thermal dissipation considerations.
These larger form factor transceivers cannot be used on the above described host boards because each slot available to a transceiver is designed to fit only single-width transceivers. To address this problem, some host boards have been designed to accommodate a fixed number of small form factor transceivers and another fixed number of larger form factor transceivers. This solution is inefficient and inflexible. Host boards designed to accommodate a fixed number of small form factor transceivers and another fixed number of larger form factor transceivers limit users to a certain number of small form factor and another certain number of larger form factor transceivers even though needs can and do change.